Retaining messages for no longer than a week or two would act as a forcing function to keep project management and comms sane.
In practice, I’ve never seen a “more-correct” system actually replace the value of long-lived chat channels and a culture of discussing things out in the open on those channels.
Long-lived chats don’t replace documentation and project management, but I’ve yet to see those replace the value of long-lived chats.
Now, it probably could be replaced by companies putting project management in a non-hellish tool that’s close to the code and has a pleasant chatting-about-issues experience and low structure so you don’t feel like you’re knocking over some PM’s sand castle if you mess with it (so NOT jira, asana, et c) but I’ve never experienced a company that does that. Communicating in the PM tools is always terrible.
It would ideally force employees to take notes and keep comms/project management sane, however I'm more likely to believe people would just get used to finding an easier workaround or guessing.